Chaotic

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The Chaotikum is in the course of the restructuring of the Precambrian proposed first era of Hadaikums . It took 163 million years, from 4,567 million to 4404 million years ago.

etymology

Magnum Chaos by Lorenzo Lotto

The term chaotic refers to the mythological chaos and the chaotic conditions that prevailed during the formation of the earth.

Definition of chaotic

Chaotic begins with the presumed beginning of the formation of the earth and the other planets of the solar system in the protoplanetary disk 4567.3 ± 0.16 million years ago. This number is based on the age that was determined using the uranium-lead method for the oldest mineral inclusions in meteorites (so-called Ca-Al-rich inclusions or CAls ). The border between the chaotic and the subsequent zirconium is temporally defined by the appearance of the oldest relics of the earth's crust. These are detritic zircon grains found in the Jack Hills of the Narryer Gneiss Terran in Western Australia ( Yilgarn Kraton ) and dated to be 4404 ± 8 million years old.

Geological events

Neither earthly rocks nor minerals have survived from the time of the Chaotic . The existing knowledge about this earliest period could therefore only be obtained indirectly, for example by examining meteorite material and moon rocks .

Despite the provisional determination of the beginning of Chaoticism at 4,567 million years before today, the exact time of the beginning of the formation of the planets (and thus the earth) is still unclear. The manganese-chromium relative dating of carbonates in carbonaceous chondrites to around 4571 million years suggests an even older age for the first solid primordial matter in the solar system. For various IAB meteorites , including the Mundrabilla meteorite from Western Australia , ages of 4570 ± 30 million years have been determined using the argon-argon method.

The condensation of solids in the form of "protoplanetary dust" enabled the so-called accretion of the planets. In the process, the dust agglomerated, probably initially due to electrostatic attraction, to form small aggregates, which above a certain mass attracted each other gravitationally and united to form so-called planetesimals and finally protoplanets .

The collision of the proto-earth with the hypothetical protoplanet Theia , which is currently considered the most likely cause of the formation of the moon , took place according to Lee et al. (1997) based on their results of the hafnium-tungsten relative dating of lunar rocks around 4510 million years ago. In the course of more recent dating using the same method, a point in time of 4527 ± 10 million years ago was determined for this event.

Outgassing and differentiation of the earth into an iron-rich earth core and a silicate-rich earth mantle may only have been completed about 4450 million years ago.

Individual evidence

  1. ^ Felix M. Gradstein et al .: On the Geologic Time Scale . In: Newsletters on Stratigraphy . tape 45 , no. 2 , April 2012, p. 171–188 , doi : 10.1127 / 0078-0421 / 2012/0020 (English, freely available online through researchgate.net ).
  2. ↑ Colin Goldblatt, KJ Zahnle, NH Sleep, EG Nisbet: The Eons of Chaos and Hades . In: Solid Earth . tape 1 , no. 1 , February 2010, ISSN  1869-9510 , p. 1–3 , doi : 10.5194 / se-1-1-2010 (English, freely available online through CiteSeer x [PDF; 261 kB ]).
  3. ↑ James N. Connelly et al .: The Absolute Chronology and Thermal Processing of Solids in the Solar Protoplanetary Disk . In: Science . tape 338 , no. 6107 , November 2, 2012, p. 651–655 , doi : 10.1126 / science.1226919 (English).
  4. ↑ Simon A. Wilde et al .: Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago . In: Nature . tape 409 , no. 6817 , January 11, 2001, p. 175–178 (English, freely available online through ucsc.edu [PDF; 202 kB ]).
  5. ↑ Alexander Shukolyukov, Günter W. Lugmair: Chronology of Asteroid Accretion and Differentiation . In: William F. Bottke u. a. (Ed.): Asteroids III . University of Arizona Press, Tucson 2002, ISBN 0-8165-2281-2 , pp. 687–695 (English, freely available online through researchgate.net ).
  6. ↑ Sidney Niemeyer: 40 Ar- 39 Ar dating of inclusions from IAB iron meteorites . In: Geochimica et Cosmochimica Acta . tape 43 , no. November 11 , 1979, ISSN  0016-7037 , pp. 1829-1840 , doi : 10.1016 / 0016-7037 (79) 90031-0 (English).
  7. ↑ Der-Chuen Lee, Alex N. Halliday, Gregory A. Snyder, Lawrence A. Taylor: Age and Origin of the Moon . In: Science . tape 278 , no. 5340 , November 7, 1997, p. 1098–1103 , doi : 10.1126 / science.278.5340.1098 (English).
  8. ↑ Anke Poiger: Date of birth of earth and moon found. Press release from ETH Zurich . In: idw-online.de. Science Information Service , November 25, 2005, accessed on August 26, 2018 .
  9. ↑ Thorsten Kleine et al .: Hf-W Chronometry of Lunar Metals and the Age and Early Differentiation of the Moon . In: Science . tape 310 , no. 5754 , December 9, 2005, p. 1671–1674 , doi : 10.1126 / science.1118842 (English, freely available online through researchgate.net ).
  10. ^ Claude Allègre et al .: The age of the Earth . In: Geochimica et Cosmochimica Acta . tape 59 , no. 8 , April 1995, ISSN  0016-7037 , pp. 1445–1456 , doi : 10.1016 / 0016-7037 (95) 00054-4 (English, freely available online from CiteSeer x [PDF; 1.7 MB ]).